1. Field of Invention
The present invention relates to a filament lamp and light irradiation heat treatment device, and particularly relates to a filament lamp used for heating an article to be treated and a light irradiation heat treatment device using the filament lamp.
2. Description of Related Art
At present, heat treatment by light irradiation from a light source is used on the occasion of various processes in a semiconductor manufacturing process, for example, film formation, oxidization, nitriding, film stabilization, silicidation, crystallization and ion injection activation. Particularly, rapid thermal processing (RTP) for rapidly increasing or decreasing the temperature of an article to be treated, for example, a semiconductor wafer, is preferably used because it can improve the throughput and quality.
In such a light irradiation type heat treatment device (hereafter, simply referred to as “heat treatment device”) for RTP, for example, a filament lamp is used as the light source.
In the filament lamp, filaments are arranged within a bulb made from a light transparent material, and 90% or greater of input power is radiated, and it is possible to heat the article W to be treated without any contact. Therefore, when the filament lamp is used as a heat source for heating a semiconductor wafer, it is possible to rapidly increase or decrease the temperature of the article to be treated compared to the resistance heating method, specifically, to increase the article to be treated, for example, to 1,000° C. or higher in several seconds to several tens of seconds; concurrently, after the light irradiation is stopped, the article to be treated can be rapidly cooled down.
One of the present inventors and his co-inventors have proposed a filament lamp having the configuration mentioned below to be used as a light source of such a light irradiation type heat treatment device (see, Japanese Unexamined Patent Application Publication 2006-279008 and corresponding U.S. Patent Application Publication 2006/0197454).
Explaining this filament lamp with reference to FIG. 8, coiled filaments 4, 5, 6 are sequentially aligned and arranged so as to extend in the tube axis direction of a bulb 1 within a straight light emitting tube whose both ends are hermetically sealed by hermetically sealed portions 2a, 2b, and internal leads 4a, 4b, 5a, 5b, 6a, 6b for electrical power supply are connected at both ends of the filaments 4, 5, 6, respectively. The internal leads of each filament extend toward both hermetically sealed portions, respectively, and are electrically connected to external leads via metal foils, individually. In other words, the internal leads 4a, 5a, 6a at one end of the filaments 4, 5, 6 are electrically connected to external leads 10a, 11a, 12a at one end via the metal foils 7a, 8a, 9a of hermetically sealed portion 2a at the respective end of the bulb 1. Similarly, internal leads 4b, 5b, 6b at the other ends are electrically connected to external leads 10b, 11b 12b via the metal foils 7b, 8b, 9b of the hermetically sealed portion 2b at the respective other end of the bulb 1. Then, the filaments 4, 5, 6 are individually connecting to feed devices 13, 14 15 via the external leads 10a, 10b, 11a, 11b, 12a, 12b, respectively.
Furthermore, an insulating tube 16 is fitted onto the internal leads 4b, 5a, 5b, 6a of the filaments 4, 5, 6, respectively, and it is placed on a section facing the filaments 4, 5, 6. Further, circular anchors 17 are arranged in parallel in the tube axis direction of the bulb 1 at positions between the inner wall of the bulb 1 and the insulating tubes 16. The filaments 4, 5, 6 are supported, for example, by two anchors, so as not to make contact with the bulb 1, respectively.
According to the heat treatment device using the filament lamp having such a configuration, since a plurality of filaments can be individually fed and luminescence of each filament can be individually controlled, even if the distribution of the degree of local temperature change, for example, on the article to be heat-treated is asymmetrical with regard to the shape of the article, light can be irradiated with the desired irradiance distribution according to the characteristic of the article to be treated, and as a result, the article to be treated can be uniformly heated; therefore, it is advantageous that uniform temperature distribution can be realized throughout the entire surface to be irradiated in the article to be treated.
For example, when RTP is conducted to a semiconductor wafer using a heat treatment device having such a filament lamp, since it becomes necessary to improve the rate of temperature increase of the article to be treated for the purpose of throughput improvement, it becomes necessary to increase the electric power to be supplied to the filament lamp more than ever before. In association with this, in the filament lamp for a heat treatment device, since it becomes necessary to apply a great electric current to the filaments, meltdown due to an excessively high temperature of the metal foils at the time of lighting the filaments has to be avoided. Consequently, it becomes necessary to widen the width of the metal foils in the direction at right angles of the tube axis of the bulb. Explaining based upon the example in FIG. 8, it becomes necessary to widen the width of the metal foils 7a, 7b, 8a, 8b, 9a, 9b in the direction at right angles of the tube axis of the bulb 1, respectively.
In order to embed the metal foils, which are wider than before, into the hermetically sealed portions, the width of the hermetically sealed portions have to be wider than before. Simply, it is believed that the width of the hermetically sealed portions can be widened by increasing the external diameter of the bulb. However, in the heat treatment device, since it is necessary to closely align and arrange many filament lamps with respect to the article to be treated in order to realize the highly accurate temperature uniformity of the article to be treated, a configuration with an increased external diameter of the bulb of the filament lamp cannot be adopted. Therefore, the conventional filament lamp shown in FIG. 8 has the problem that metal foils made wider than before cannot be arranged in the hermetically sealed portions.
As described above, in the filament lamps for the heat treatment device, the width of the metal foils to be arranged in the hermetically sealed portions needs to be wider than before while the external diameter of the bulb of the filament lamps needs to be the same level or smaller. Satisfaction of such contradictory requirements is difficult with the conventional filament lamp.